Air Pollution Exposure Studies in Smokers and People with Chronic Obstructive Pulmonary Disease

People with chronic obstructive pulmonary disease (COPD) are often thought to be especially at risk from air pollution and thus are prime candidates for clinical exposure studies. However, scientific, ethical, legal, and practical problems must be faced in studying individuals with COPD. To deal with these problems, the following priorities of concern are suggested: (1) the safety and welfare of subjects, (2) scientific rigor of the experiment, (3) relevance of the experimental results to “real-world” health concerns, that is, to air quality regulatory decisions, and (4) improved general understanding of physiology or toxicology. Smoking often complicates interpretation of the results of clinical exposure studies; in many cases, smokers should be excluded to maximize scientific rigor. However, smokers may be viewed as a group with early or mild COPD: most have at least slight chronic bronchitis. Thus, in some investigations, smokers might be appropriate surrogates for diseased population groups. Care should be taken to distinguish between the effects of the experimental pollutant and the effects of recent smoking on smokers' experimental responses. Only a few of many potential ambient-air hazards have been investigated in people with COPD; no clear differences in responses from healthy people have been found. Only a few studies have attempted rigorous comparisons between smoking and nonsmoking subjects, either healthy or with lung disease. Their results have been inconclusive.